Synchronization system for watches

ABSTRACT

Synchronizing pulses from a frequency divider are applied to a coil-magnet system to maintain vibration of a quartz crystal controlled watch. The pulses are applied at particular time relationships with respect to the rest or zero position of a vibrator during each forward and backward movement to energize a drive coil controlled by a switch.

United States Patent [191 [111 3,859,781

Sauer Jan. 14, 1975 [5 SYNCHRONIZATION SYSTEM FOR 3,212,252 10/1965 Nakai 58/23 R WATCHES [75] Inventor: Wolfgang Sauer, Freiburg, Germany Primary Examiner-Edith Simmons Jackmon Attorney, Agent, or Firm-John T. OHalloran; [73] Asslgnee' Indusmes New York Menotti J. Lombardi, Jr,; Edward Goldberg [22] Filed: July 23, 1973 [21] Appl. No.: 381,649 ABSTRACT Synchronizing pulses from a frequency divider are ap- [52] US. Cl. 58/28 A, 318/129 plied to a coil-magnet system to maintain vibration of lllt- Cl G04) H02k P a quartz crystal controlled watch. The pulses are ap- Field Of 23 A, 23 AC, 23 TF, plied at particular time relationships with respect to 58/28 R, 28 A, 23 B; 318/129; 331/15 the rest or zero position of a vibrator during each for- 331/] 16 M ward and backward movement to energize a drive coil controlled by a switch. [56] References Cited UNITED STATES PATENTS 5 Claims, 9 Drawing Figures 3,124,73] 3/1964 Eysen et al. 58/28 A s Stage n Stage 2 Stagel [L 5 A Tr A I i BlnaryFreque cy y 4 D gasgafitlc 2 2 59 I E" fle: E:- S tor Flop Flop Flop Flop L L l= P LS T, Quartz J SYNCHRONIZATION SYSTEM FOR WATCHES BACKGROUND OF THE INVENTION l. Field of the Invention The present invention concerns an improved synchronization system applicable to both conventional contact-controlled clocks and eiectronically driven clocks with oneor two-coil systems.

2. Description of the Prior Art The step-by-step switches primarily considered for use as electromechanical transducers in utility-type crystal-controlled clocks and particularly in crystalcontrolled wrist watches are relatively sensitive to shock. Electromagnetically driven balance or tuningfork systems show a much better behavior in this respect. For manufacturing reasons, too, a crystalcontrolled clock is very advantageous in which use is made of an already existing clockwork. Simply by installing commercially available crystal oscillators and frequency dividers, this clockwork is extended to a utility type crystal-controlled clock by synchronizing the vibrator frequency of the existing clockwork by means of the divided crystal frequency.

Since the vibration frequency of a balance depends on, among other things, the kind of energy supply, this fact, which is disadvantageous in itself, can be used to synchronize an electromagnetically driven clock vibrator. It is known that a simple oneor two-coil balance system driven automatically by a suitable circuit can be synchronized if, in addition to the main drive pulse, one or more time-shifted, and thus adjacent, auxiliary drive pulses are applied which are triggered by the sync signal occurring several times during a vibration of the balance. The frequency of the sync pulses is thus several times higher than that of the balance. In that method, however, more power than necessary is applied to the balance system through the auxiliary drive pulses, so that the balances vibration amplitude increases and the battery is additionally loaded, while undesirable transient conditions may occur during the control.

On the other hand, it is known that the vibration frequency of an electromagnetic balance system can be better synchronized if the drive coil is supplied with two successive drive current pulses having a constant total energy content, one of which is applied before the reference position of the balance, and the other thereafter, the vibration frequency of the balance being changed as a function of the sync signal by variation of the relative amplitude values of the two pulses.

For the realization of that method, however, a complicated and expensive circuit is required which comprises a bridge push-pull stage, designed to drive the electromagnetic balance system, and two moving coils, which cannot be connected directly to one pole of the battery as is desirable if such circuits are to use monolithic integrated techniques. In addition, the bridge push-pull circuit is not capable of also maintaining the vibrations of the balance without the circuit generating the sync signal.

In addition, the overall circuit of this known type opcrates on the principle of phase comparison between the vibration frequency of the balance and the fre quency of the sync signal. It therefore has several multivibrator stages and a sawtooth generator for carrying out the phase comparison, which add to the complexity mentioned above. In addition, the known circuit is designed for a special coil and magnet system with two concentric pancake coils and a pair of magnetic poles in the direction of vibration, so that, in the coil legs located before and behind the reference position, one positive and one negative pulse are generated with each semi-vibration of the balance, which thus makes necessary the use of the above-mentioned bridge push-pull circuit.

Lastly, a method of synchronizing clock vibrators is known which also uses a phase comparison. Similarly, in that case, the frequency of the sync signal is several times higher than that of the vibrator. Also, sharp sync signals are used which only excite the circuit maintaining the vibrations to deliver the drive current pulse. Provision is also made so that the drive current pulse is stopped by a second sharp sync pulse shifted in phase with respect to the triggering sync pulse.

This known synchronization method, also requires an extensive electronic circuit, particularly for deriving the setting signals by phase comparison, and two twocoil systems, one of which serves as the drive system and the other as the pick-up system for the phase comparison.

SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a synchronization system which is universally applicable to contact-controlled clocks and electronic clocks. The apparatus synchronizes mechanical vibrators of utility clocks and wrist watches which are driven by a coil-magnet system controlled by a crystal oscillator frequency divided down to the order of magnitude of the frequency of the mechanical vibrator. A current pulse for maintaining the vibration is applied via a mechanical or electronic switch to the drive coil during each forward and backward movement of the vibrator, the drive coil thus being traversed by a drive current pulse. Only one simple coupling element establishes the connection to the works of the contact-controlled clock or of the electronic clock. The forwardmovement drive pulse and the backward-movement drive pulse are applied to the drive coil either at a different distance from the rest position of the vibrator before or after its rest position or at the same or a different distance before and after the rest position of the vibrator. The drive energy is divided between the forward-movement and the backward-movement drive pulse depending on the deviation of the divided crystaloscillator frequency from the frequency of the mechanical vibrator or from an integral part or multiple thereof.

The known synchronizing arrangements can thus be considerably simplified if the synchronization does not act upon each pulse of the induced voltage separately, but if the forwardand backward-movement drive pulses are utilized for the synchronization depending upon the deviation of each from the rated frequency. The division of the drive energy between the forwardmovement pulse and the backward-movement pulse also means a division in which, the total drive energy is not constant.

In one embodiment of the invention, the application of the forwardand backward-movement pulses is advantageously realized by displacing the central axes of the drive coil from the magnet system in a parallelstaggered arrangement when the vibrator is in the rest position. This displacement offers an advantage in coilmagnet systems with an odd number of pairs of magnetic poles and particularly with a single pair of magnetic poles. The parallel stagger or displacement of the central axes of the drive coil and the magnet system may be dispensed with in magnet systems with several pairs of magnetic poles if the main pulse of the voltage induced in the drive coil by such multi-magnet systems is utilized for the pulse supply in addition to one or more secondary pulses.

In another embodiment of the invention, the division of the drive energy between the forward-movement pulse and the backward-movement pulse depending on the deviation of the divided crystal-oscillator frequency from the frequency of the mechanical vibrator or from an integral part or multiple thereof is realized by turning off or weakening the current flow in the mechanical or electronic switch periodically with the sync frequency for a period of time which is smaller than the smallest time duration between the drive pulses occurring during each semi-vibration. This occurs between the forward-movement pulse and the backwardmovement pulse.

If the sync signal is made rectangular for this purpose, its mark-to-space or on-off ratio must only be chosen, according to the smallest time between the drive pulses occurring during each semi-vibration, or between the forward-movement pulse and the backward-movement pulse of the vibrator. The setting of this mark-to-space ratio can be done in a simple manner with the existing frequency divider by applying a logic operation to the width of the output pulse of the frequency divider and the width of the output pulse of preceding divider stages via a NAND-circuit or a flipflop, so that he output pulse of the frequency divider no longer has a unity or one to one on-off ratio, but that the width of the output pulse is determined by the absolute width of the output pulse of one of the preceding frequency divider stages, which output pulse is delivered with a unity ratio. The circuit arrangement for the invention includes a transistor which is switched by the rectangular sync signal, is connected in series with the mechanical or electronic switch, and is turned on and off by the sync signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. la and 1b schematically show variations of the essential part of the drive system of the works of a contact-controlled clock and of an electronic clock;

FIG. 2 shows various waveforms to explain the principle of operation of the invention;

FIG. 3 shows the various possible time slots of the drive current pulses;

FIG. 4 shows a block diagram of a clock system in accordance with the invention;

FIG. 5 shows several waveforms occurring with the clock of FIG. 4;

FIG. 6a and 6b schematically show top and side views of the balance wheel system of the clock used in the arrangement of FIG. 4; and

FIG. 7 shows waveforms of the magnetic induction and the voltage induced in the control coil for several magnetic systems.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. la shows the drive coil L and the contact S of the works of a contact-controlled clock. The coil L cooperates with a magnet system which, may have one, two, or more pairs of magnetic poles.

If, as is usually the case in contact-controlled clocks, the contact is closed by the movement of the balance, the coil is traversed by a current which acts upon the magnetic poles, thus driving the balance. On the other hand, however, the magnets also induce a voltage in the coil on which the voltage drop developed across the coil due to the current flow is superposed, as indicated in FIG. 2b by the brokenline. In FIG. 1, this induced voltage is designated u,-,,.

FIG. lb-shows the essential part of an electronic balance system, namely the drive coil L and the transistor Tr. In a one-coil circuit, this transistor is turned on and off via a second transistor. In a two-coil circuit, it is turned on and off by the voltage induced in the control coil. Also in the case of an electronic clock drive, the magnet in the coil L generates the induced voltage u,-,,, on which the voltage drop developed across the coil due to the current flow is superposed.

FIG. 2a shows the amplitude response a of the mechanical vibrator as a sinusoidal curve of the amplitude A. If the support of the vibrator has no friction losses, the vibration, once excited, would be maintained unchanged. In FIG. 2a, the undisturbed duration of this mechanical vibration is designated T If, in magnet systems with odd numbers of pairs of magnetic poles, a displacement or parallel stagger of the coil axis and the magnet system axis insure that the drive pulses during the forwardand backwardmovements occur asymmetrically in relation to the rest position of the vibrator, the vibrator frequency will vary according to the formula T= T ATI A72. The actual vibration duration I is, therefore, composed of the sum of the undisturbed vibration duration T and the periods-ATI and A72, with the signs being taken into account. The period ATl is the period from the undisturbed zero crossing up to the intersection of the zero line and the tangent to the sinusoidal curve changed by the drive pulse I-I occurring during the forward-movement, while the period ATZ is the period between the next undisturbed zero crossing and the preceding intersection of the zero line and the tangent to the sinusoidal curve changed by the drive pulse R occurring during the backward movement, which period must therefore have a negative sign in the formula given.

FIGS. 2b and 2c show the pulses H, R of the induced voltage u, and of the associated pulse current i flowing in the coil, which occur asymmetrically in relation to the zero position of the mechanical oscillator, as a function of the time t. The horizontal dash-and-dot line of FIG. 2a indicates the displacement of the central axes of the coil and magnet systems.

If the collector-emitter path of an additional transistor is connected in series with the series connection of the drive coil and the mechanical switch S or the transistor Tr of FIG. 1, the base of which additional transistor is controlled by a sync signal having the on-off characteristic of FIG. 3a, the various operating conditions shown in FIGS. 3b to 3g are obtained. Current flows in the coil L in the on-condition, shown by the longer pulse portion of FIG. 3a, and the current flow is interrupted in the off-condition, shown by the shorter positive pulse portion of FIG. 3a, due to the sync signal which has the duration T,. It is also possible, however,

to reduce the current flow through the additional transistor to a suitable partial current instead of turning it off completely. This may be done, for example, with a resistor connected in parallel to the collector-emitter path of the additional transistor.

FIGS. 3b and 3c show the drive current pulses where the vibrator vibrates at the rated frequency. In FIG. 3b, the off-pulse, shown by dotted lines, lies in the center of the greater distance between two successive drive pulses, or between the return-movement pulse R of one vibration and the forward-movement pulse H of the next vibration. In contrast, FIG. 3c shows the position of the drive current pulses in which the smaller distance between two successive drive pulses, between the forward-movement pulse and the backward-movement pulse of one and the same vibration, lies approximately in the center of the off-signal.

It should be pointed out that these two operating conditions shown are not synchronized conditions. On the contrary, since the vibrator vibrates at the rated frequency, the synchronization has no effect on these conditions. An advantage of this characteristic is that a clock using this method can be set to the rated frequency, and is not necessary to predetermine a particular frequency deviation in order for the synchronization to become effective.

On the contrary, the synchronization does not become effective until the vibrator does not vibrate at the rated frequency, which cases are shown in FIGS. 3d to 3g. In FIG. 3d, the forward-movement drive pulse H, which makes the period longer and causes the frequency to decrease, is suppressed by the off-signal, and only the backward-movement pulse R becomes effective. This makes the period shorter and causes the frequency to increase. As a result, this pulse travels to the left during several periods as indicated by the arrow AV directed to the left. This travelling can be made visible very clearly on the screen of an oscilloscope.

The synchronized condition resulting from this increase in frequency is shown in FIG. 3e. The two pulses of a forward movement and a backward movement are shifted with respect to the off-portion of the sync signal so that the frequency-increasing pulse R has traveled to the left and that the frequency-decreasing pulse H becomes effective again at least partly. Thus, the inventive division of the drive energy between the forwardmovement pulse and the backward-movement pulse has taken place. This synchronized condition is indicated in FIG. 3e by the formula AV 0, where AV is characteristic of the relative speed between the sync signal and the drive current pulse and is visible on an oscilloscope screen as mentioned above.

From this synchronized condition, in which the mechanical vibrator is now forced to vibrate at the rated frequency, the vibrator can then return to a condition as shown in FIGS. 3b and 3c if it is caused to freely oscillate on its own again at the rated frequency by some external influence.

FIGS. 3f and 3g show the other possible case of synchronization in which the period-lengthening and frequency-decreasing forward-movement drive pulse H is effective, while the period-shortening and frequencyincreasing drive pulse R, occurring during the backward movement, is suppressed. In this case. the forward-movement drive pulse H travels" to the right during several vibrations, as indicated by the arrow AV directed to the right, until the condition of FIG. 3g is achieved in which a more or less large portion of the backward-movement drive pulse R becoms effective again. This synchronized condition also corresponds to the case AV 0. In this synchronized condition, as in the case of FIG. 36, the mechanical vibrator is operated with the rated frequency by force, which condition it can leave only if it gets back into a condition on its own in which it vibrates at the rated frequency.

From the description of the various operating conditions, it can be seen that the vibrator is caused to vibrate at the rated frequency for all conceivable operating conditions, either vibrating at the rated frequency itself or being forced to do so. If, in the case of a wrist watch, movements of the arm or shocks cause the balance to change its frequency, the pulses can leave the synchronized condition but are always returned thereto by the method according to the invention, except if the shock or the movement of the arms causes the vibrator to vibrate freely at the rated frequency. In this condition, as was explained in detail, no synchronization takes place because it is not necessary. The method according to the invention is, therefore, adapted exactly to the respective operating condition.

As mentioned above, the system uses only the subassemblies normally required for a crystal-controlled clock, namely the crystal oscillator, the frequency divider, and the remainder of the simple balance system, and utilizes the two existing characteristics in an advantageous manner, with only one additional transistor required as an electronic switch controlled by the sync signal. Since available monolithic integrated clock frequency dividers usually contain the above-mentioned NAND or flip-flop stages, with which the width of the output pulse is adapted to the current-flow duration of step-by-step switches or stepping motors, these clock frequency dividers may be readily used for synchronization with this system.

FIG. 4 shows the block diagram of a clock built according to the principles of the invention. FIG. 4 includes an oscillator I with a quartz crystal 2, a binary frequency divider 3 and a reset-set, RS-flip-flop 4. This circuit element generates the pulses necessary for the synchronization of a common clock/watch.

The waveforms of the pulses are shown in FIG. 5. It is assumed that stage 1 of the binary frequency divider at the output has an output frequency of 4 Hz for synchronizing the clock/watch balance wheel which also has a nominal frequency of 4 Hz. The binary frequency divider 3 contains n stages consisting of flip-flops. Thus at point A of stage 1 the output signal has the waveform shown at A in FIG. 5 which is in the form ofa rectangular wave with a pulse duty factor of 0.5. At point B and thus at the output of stage 2 there is a rectangular signal with a frequency of 8 Hz. At point C and thus at the input of stage 2 there is a rectangular signal with a frequency of 16 Hz. These two waveforms are also shown in FIG. 5, waveform B further showing the inverted signal existing at the other output of the flip-flop of stage 2. This inverted output signal is fed to the reset input R of the RS-flip-flop 4. The output signal of stage 1 is fed to the set input S of the RS-flip-flop 4. Therefore, each leading edge of waveform A switches on the RS- flip-flop and each following leading edge of waveform B switches it off. Thus, at output D, the waveform shown at D in FIG. 5 is generated.

This output signal is fed to the base of transistor T1 the emitter of which is connected to the zero or ground point of the circuit and the collector of which is connected to the voltage-conducting pole of the supply voltage source U across the driving coil L and the emitter-collector path of the transistor Tr. The current flow of transistor T, is, therefore, impossible during the negative pulse portions of waveform D.

Besides the drive coil L the right side of the circuit shown in FIG. 4 contains the control coil L connecting the base to the emitter of transistor T As schematically shown in FIGS. 6a and 6b, the magnetic system rotates over the two coils. In FIG. 6b the balance wheel U consists of the two discs S1 fixed to shaft W to which is also fixed one end of the spiral spring Sp outside of the space formed by the two discs. The other end of the spiral spring is fixed to the works platine of the clock- /watch.

The magnets M of the magnetic system are fixed to each disc S1 opposite each other. Diametrically opposite the magnets, are two counterweights G also fixed to each disc S1. The magnets M cooperate electrodynamically with the coil systems L L which lies within the space between the magnets M whenever the balance wheel is in its zero position. Furthermore, FIGS. 64: shows that in the zero position of the balance wheel U the magnets M are displaced by the angle a with respect to the center of the coil system as mentioned above for magnetic systems with an odd number of magnetic pole pairs.

FIGS. 7a, 7b and 70 show several waveforms of the magnetic induction B and of the voltage u induced in the control coil L which occur with magnetic systems having one (FIG. 7a), two (FIG. 7b) or three (FIG. 70) magnetic pole pairs. These magnetic pole pairs are contiguously arranged on the balance wheel shown in FIG. 6 and have the polarities of their magnets as shown in FIGS. 7a, 7b and 70. In FIG. 7 it is assumed that the control coil L moves from left to right at the speed v through the magnetic field formed by the magnets. Thus, the waveforms of the magnetic induction B and the induced voltage 14, are generated.

During both directions of movement, the induced voltage has the same voltage waveform if a oneor a three-magnet system is used. If a two-magnet system is used, the polarity of the induced voltage is inverted with the moving direction. Thus, in one direction, the waveform of the induced voltage u,-,, is as shown in FIG. 7b and in the opposite direction of movement the waveform is reversed thereto with respect to the x-axis. Therefore, the negative pulse portion existing at x during one direction is positive during the opposite direction. Also the two positive pulse portions to the left and right ofx 0 for one direction are negative for the opposite direction. As a result, if a two-magnet system is chosen, the angle a mentioned above is not necessary.

What is claimed is:

l. A system for synchronizing mechanical vibrators of clocks and watches comprising a rotatable balance wheel including a pair of spaced discs rotatable together on a common shaft, each disc having a respective magnet mounted thereon and aligned with the other said magnet, said wheel and magnet having a given rest position, electromagnetic driving means positioned adjacent said wheel and magnet, said wheel rotating backward and forward with respect to the position of said driving means and having a nominal frequency, said driving means including a driving coil and control coil positioned between said discs and magnets and having a common center angularly displaced from said rest position, switching means for applying driving pulses to said driving means, a crystal oscillator and frequency divider providing synchronizing pulses substantially equal in frequency to the nominal frequency of said balance wheel, and control means for applying said synchronizing pulses to said switching means during each forward and backward movement of said balance wheel, said switching means and driving means maintaining the frequency of said balance wheel.

2. The system of claim 1 wherein said switching means includes a first transistor connected between said control means and said driving means, said control means includes a flip-flop circuit, and means supplying a first pulse input signal to said flip-flop circuit equal in frequency to said nominal frequency and a second pulse input signal equal in frequency to twice said nominal frequency.

3. The system of claim 2 including a second transistor connected across said control coil and in series with said driver coil and first transistor.

4. The system of claim 3 wherein said discs include magnets having an odd number of magnetic pole pairs.

5. The system of claim 5 wherein said switching means is turned off periodically by said synchronizing pulses at said frequency for a period of time which is smaller than the smallest time between the forward and backward movement drive pulses, said synchronizing pulses being applied to maintain said frequency only when said balance wheel is not at said frequency.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,859,781 Dated January 14, 1975 Inventor(s) Wolfgang Sauer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title page, insert E32 Priority August 4, 1972 Germany Signed and sealed this 1st day of April 1975.

n 7 1' Gears):

AtteSt: I

' C. MKRSHALL DANN RUTH C, MASON Coxm'-.1issioner of Patents Eattesting Officer a Trademarks ORM PO-IOSO (10-69) USCOMM-DC GOZHG-PQQ LLS. GOVERNMENT PRINTING OFFICE I969 (f 4564 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pat t No, 3,859,781 Dated January 14, 1975 Inventor(s) Wolfgang Sauer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title page, insert [32 Priority August 4, 1972 Germany En] P 22 38 405.0

Signed and sealed this 1st day of April 1975.

Attest C 1A SHALL DAITN RUTH C, KIASOP-I Commissioner of Patents attesting Officer and Trademark S ORM PO-IOSO (10-69) USCOMM-DC soars-P69 UvS. GOVERNMENT PR NTING OFFICE 1969 -55'6-3 

1. A system for synchronizing mechanical vibrators of clocks and watches comprising a rotatable balance wheel including a pair of spaced discs rotatable together on a common shaft, each disc having a respective magnet mounted thereon and aligned with the other said magnet, said wheel and magnet having a given rest position, electromagnetic driving means positioned adjacent said wheel and magnet, said wheel rotating backward and forward with respect to the position of said driving means and having a nominal frequency, said driving means including a driving coil and control coil positioned between said discs and magnets and having a common center angularly displaced from said rest position, switching means for applying driving pulses to said driving means, a crystal oscillator and frequency divider providing synchronizing pulses substantially equal in frequency to the nominal frequency of said balance wheel, and control means for applying said synchronizing pulses to said switching means during each forward and backward movement of said balance wheel, said switching means and driving means maintaining the frequency of said balance wheel.
 2. The system of claim 1 wherein said switching means includes a first transistor connected between said control means and said driving means, said control means includes a flip-flop circuit, and means supplying a first pulse input signal to said flip-flop circuit equal in frequency to said nominal frequency and a second pulse input signal equal in frequency to twice said nominal frequency.
 3. The system of claim 2 including a second transistor connected across said control coil and in series with said driver coil and first transistor.
 4. The system of claim 3 wherein said discs include magnets having an odd number of magnetic pole pairs.
 5. The system of claim 5 wherein said switching means is turned off periodically by said synchronizing pulses at said frequency for a period of time which is smaller than the smallest time between the forward and backward movement drive pulses, said synchronizing pulses being applied to maintain said frequency only when said balance wheel is not at said frequency. 